Did Santa forget to put an iPhone 4S in your stocking? Are you feeling like you missed out on Siri? Have no fear, for there is one forgotten gift under the tree, and it’s from the iOS jailbreak community. Cydia developers chpwn and Ryan Petrich have collaborated on the first 100% legit, 100% legal port of Siri. Unfortunately, there is a catch: you’ll still need those live authentication tokens from an iPhone 4S.

The Siri port is called Spire, and it’s available now in Cydia. It can be installed on any jailbroken device that runs iOS 5. After the initial download, the free app will install and then download about 100MB more data (the actual Siri files). After the installation is complete, a working version of Siri will be so close, yet so far.

The catch is that Apple only allows Siri requests from the iPhone 4S. The 4S contains an ID token that tells Apple that it is indeed the latest handset that’s trying to access Siri. One way around this to set up a Siri Proxy using a 4S that belongs to you or a friend. Spire has a field that lets you enter the proxy info and complete the port of Siri.

The developers of Spire also speculate that there will soon be commercial services that will charge customers to use a Siri proxy. This would rid you of the requirement of hacking a friend’s iPhone, and let you have Siri by simply paying a monthly fee. If a) this happens, and b) the fees are reasonable, then this would be an attractive alternative to forking over for an iPhone 4S.

Right now Spire isn’t going to be for most users. Setting up a Siri proxy requires some know-how (not to mention an iPhone 4S). Until those commercial Siri proxies start popping up, Spire will be for advanced users only.